Apparatus for die-casting metals

ABSTRACT

Die-casting apparatus, primarily for casting ferrous metals, including a shot duct formed from two or more longitudinally successive structurally separate components which may be made of respective different materials or of the same material, in either case selected to suit the operating conditions to which they are exposed. The components are supported partly by one of the dies and partly by a casing such that the degree of tightness of interference between the casing and the components supported therein is selected to provide a controlled degree of radially outward conduction of heat thereby to control the operating environment of the components.

United States Patent Carver et al.

[is] 3,685,572 [451 Aug. 22, 1972 [541 APPARATUS FOR DIE-CASTING METALS[72] Inventors: Bryan George Carver, Birmingham;

Ronald Crooks, Wolverhampton,

both of England [73] Assignee: G.K.N. Group Services Limited,

Worcestershire, England [22] Filed: Oct. 19, 1970 [21] App1.No.: 81,801

[30] Foreign Application Priority Data Oct. 25, 1969 Great Britain..52,377/69 52 U.s.c1 ..l64/312 51 Int. Cl. ..B22d 17/04 [58] Field ofSearch ..164/303, 306, 309, 312, 313,

127,136, 47, 284, 62; 18/12 P, 5 BE, 5 B], 30 FN, 30 PF, 30 QM, 30 QB,DIG. 35

[56] References Cited UNITED STATES PATENTS 3,516,480 6/1970 Woltering..l64/312 3,515,203 6/1970 Parlanti ..'l 8/ 30 0? 3,015,849 1] 1962Mittelstadt ..'.164/3 14 X 3,533,464 10/1970 Parlanti ..164/3123,540,519 11/1970 Yates ..l64/138 3,270,383 9/1966 Hall 164/3 14 XPrimary ExaminerJ. Spencer Overholser Assistant Examiner-John S. BrownAttorney-Milton J. Wayne [57] ABSTRACT Die-casting apparatus, primarilyfor casting ferrous metals, including a shot duct formed from two ormore longitudinally successive structurally separate components whichmay be made of respective different materials or of the same material,in either case selected to suit the operating conditions to which theyare exposed. The components are supported partly by one of the dies andpartly by a casing such that the degree of tightness of interferencebetween the casing and the components supported therein is selected toprovide a controlled degree of radially outward conduction of heatthereby to control the operating environment of the components.

5 Clains, 2 Drawing Figures APPARATUS FOR DIE-CASTING METALS BACKGROUNDOF THE INVENTION 1. Field of the Invention This invention relates to anapparatus for casting metal into a cavity formed between separablerepeatedly usable dies and in which shots of molten metal are fed intothe cavity under pressure, as distinct from merely under gravity, alonga duct (herein called the shot duct) by a piston movable therein, saidshot duct communicating at one end (herein called the delivery station)with the die cavity, and being so formed or constructed as to be able toreceive at another position (herein called the receiving station) spacedlongitudinally of the shot duct from the delivery station, a quantity ofthe molten metal to be fed along the shot duct into the die cavity. Suchapparatus is hereinafter referred to as die-casting apparatus of thekind specified.

The invention is applicable primarily to die-casting apparatus of thekind specified for casting ferrous metal, that is cast iron or steel,but may be applied generally to apparatus for casting other metals, moreespecially those in relation to which similar or analogous problems tothose hereinafter described arise.

2. Description of the Prior Art Ferrous metals require to be cast at ahigh temperature which typically is the region of 1,300 C for cast ironand in the region of l,600 C for steel.

Previously the shot duct either has been formed as a single tubularcomponent or as incorporated a onepiece liner extending throughout thelength of the shot duct.

The conveying of a ferrous metal at these temperatures along the shotduct has been found to produce rapid deterioration of the shot ductleading to a shortened service life, but the deterioration phenomenawhich we have observed are consistent with the deterioration arisingfrom somewhat different causes at different positions along the shotduct. The present invention is based on the concept that a shot ductwhich is better able to withstand these conditions of service requiresto be designed to take into account the different conditions ofoperation which occur along its length and the present invention is,therefore, based in part upon careful observance and analysis of theseconditions of operation as well as upon the structure of the improvedshot duct designed to overcome this problem.

In particular it has been observed that at the delivery station theinterior surface of the shot duct tends to be eroded by penetration intothe surface layer of pieces of a solid state skin formed on the moltenmetal immediately adjacent to the inner surface of the shot duct, duepossibly to the breaking up of this skin during the forcing of the shotof molten metal by the piston along the shot duct and into the diecavity.

The action of the solidified skin on the surface layers of the materialof which the shot duct is composed is partly analogous to abrasion by asolid state abrasive substance, and partly analogous to theestablishment of elementary friction welds particularly if the materialutilized for the shot duct is a metal having welding compatability withthe metal undergoing casting.

In contrast with this it has been observed that the interior surface ofthe shot duct at the receiving station is consistent with physicaland/or chemical erosion by impact and contact with the molten metal tobe cast when the latter is first delivered into the shot duct.

For example, there is marked erosion in a region of impact of the moltenmetal at the receiving station on the interior surface of the shot duct(such metal being delivered thereinto through an opening formedconveniently in the upper wall of the shot duct) when the cast metal iscast iron and the shot duct is formed of steel. It is believed that thiserosion is due to the greater percentage of carbon present in the castiron than in the steel, the iron constituent of the latter tending tobecome transferred to the cast-iron to bring about a greater degree ofequality in the carbon concentration of the two metals.

Erosion at the region of impact is also believed due to fluid frictionbetween the molten metal to be cast and the solid state material ofwhich the shot duct is composed.

An intermediate section of the shot duct lying between the delivery andreceiving stations is also subjected to deterioration which tends totake place by SUMMARY OF THE INVENTION Based on these observations, ashot duct in accordance with the present invention is sub-divided intolongitudinally successive structurally separate. components, thematerials of which are selected respectively to suit the differentoperating conditions to which these components are subjected during feedof themolten metal along the shot duct to the die cavity.

A preferred embodiment of shot duct in accordance with the invention isformed as an assembly of longitudinally successive structurally separatecomponents, there being one such component at the delivery station andformed of a material which is selected to present a hard surface at theoperating temperature resistant to penetration by fragmentation anddisplacement of a solid state skin formed in the metal undergoingcasting and a further such component at the receiving station which ismade from a material which does not enter into chemical and/or physicalreaction with the metal undergoing casting.

Thus it is contemplated that the shot duct may include a component atthe delivery station formed of a material which is selected to present ahard surface at the operation temperature resistant to penetration byfragmentation and displacement of a solid state skin formed in the steelundergoing casting adjacent to the interior surface of the shot duct atthis station.

The component incorporated in the shot duct at the receiving stationmay, on the other hand, be made from a material which does not enterinto a metallurgical reaction with the metal undergoing casting. Thematerial may either not include the metal to be cast or include suchmetal only in combination with one or more alloying elements whichprovide a high degree of stability preventing or reducing migration ofthe metal The component of the shot duct incorporated therein at thedelivery station is preferably made of a material selected to present arelatively low thermal otherwise tend to reduce the hardness of thesurface.

The shot duct preferably includes an intermediate component betweenthose situated at the delivery and receiving station, such intermediatecomponent being formed from a material selected to have good resistanceto thermal fatigue.

A further feature of the invention is that one or more of the componentsabove described may be mounted in a casing supporting the componentsexternally and made of a material and to dimensions which provide alone,or in combination with the components, the requisite transverse rupturestrength.

This permits one or more of the components to be made of a materialwhich would not necessarily present the required transverse rupturestrength but is,

' nevertheless, suited to the operating conditions arising from thepresence of the molten metal and its movement along the interior of theshot duct.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described,by way of example, with reference to the accompanying drawings wherein xFIG. 1 shows diagrammatically an injection moulding machine in sideelevation, and

FIG. 2 shows a vertical cross-section through the axis of the shot ductthereof on a larger scale.

DESCRIPTION OF THE PREFERRED EMBODIMENT- As seen in FIG. "2, theapparatus comprises separable dies and 11 which define a die cavity 12and which separate along a parting plane X. Such dies can be movedbetween a closed position, as shown in FIG. 2, and an open position inwhich the die 11 moves to the left away from the die 10 by any suitablemechanism, either mechanical or hydraulic, of known form.

FIG. 1 shows a known form of machine employing a mechanical mechanismfor closure of the dies 10 and 11. This machine includes a bed 1 havinga mounting member 2 which carries the die 10 in a fixed position. Themovable die 1 1 is carried on a slide plate 3 which is slidable alonghorizontally extending bars 4 which are fixed in position relative tothe bed 1. The slide plate 3 is movable along the bars 5 by means of atoggle mechanism indicated generally at 5. The toggle mechanism 5 isoperable by means of a piston and cylinder unit 6 which is carried by alongitudinally adjustable mounting member 7. A connecting rod 60extends'from the unit 6 to the toggle mechanism 5. Also fixedly mountedon the bed 1 there is a piston and cylinder unit 8 having a connectingrod 80 for operation of the shot duct 14 which is hereinafter describedin detail.

The dies 10 and 11 are made of a material which is capable of repeateduse to form cast metal articles in the die cavity 12.

When the metal to becast is a ferrous metal, such as cast iron or steel,the dies 10 and 11 are either made of, or lined with, a metal of ahigher melting point, or have a rate of heat dissipation, either naturalor produced by cooling means provided in association therewith, whichmaintain them at a sufficiently low temperature to ena- 1 ble them towithstand repeated use. Typically the dies may be formed of molybdenumor an alloy thereof.

Preparatory to casting metal into the die cavity 12, a

medium may be sprayed onto the surface of the die cavity to facilitatestripping the cast article therefrom and a suitable medium for thispurpose is graphite suspended in 'a suitable carrier, or carbon blackdeposited from an acetylene torch.

One or both of the dies is formed with a channel or gate 13 by means ofwhich the metal to be castis fed into the die cavity upwardly,preferably into the lower- 7 most part of the die cavity.

The metal is fed to the lower end of the gate 13 by 7 means of the shotduct 14, and which is formed or constructed to define a horizontal, orapproximately horizontal, bore 15 conveniently of circular shape incross-section and of uniform diameter throughout its length (except fora terminal portion at the forward end as hereinafter described). In somecases the bore 15 could, however, be inclined to the horizontal.

The cast metal is delivered into the bore 15 at a receiving station 16andis moved'along the bore by a piston '17 connectedto a suitableoperating mechanism, either mechanical or hydraulic, and such as thepiston and cylinder unit 8. The metal thus is forced from the bore 15 ata delivery station 18 to pass upwardly through the gate 13 underpressure.

The pressures employed may vary widely but it is contemplated thatpressures of as much as 5,000 to 6,000 lbs. per square inch may beobtained during the operation of feeding the molten metal into the diecavi-- Again delivery of molten metal into the bore may be effected in avariety of ways, one of which is illustrated diagrammatically andconsists in pouring the metal A from a pot l9 through'an opening 20leading to the" receiving station 16, the metal being at the requiredtemperature, for example in the region of l,300 C for cast iron andl,600 C for steel, by any suitable heating means provided in associatedwith the pot Referring now specifically to the construction of the Ishot duct 14, this comprises a plurality of inner components, thesebeing a front liner or insert 21 at the delivery station, anintermediate liner or insert 22, and

The front casing component 24 has a'tits forward end a flange 30 throughrespective apertures in whichscrews 31 are passed to secure the frontcasing component 24 to the fixed die 10. The front casing component 24includes a generally tubular body portion within which part of thegenerally tubular rear casing component 25 is received. The rear casingcomponent 25 has an external flange 35 mid-way along its length. Theflange 35 abuts the rear end of the front casing component 24 and isapertured for the passage of screws 34 whereby the casing components 24and 25 are rigidly secured together.

The front liner or insert 21 is located in an aperture in the fixed dieand is largely supported thereby. However, the insert 21 extendsoutwardly from the fixed die 10 and at its rearward end is supportedparticularly by the flange 30 of the forward casing component 24. At itsrearward, the insert 21 is formed with an outwardly directed flange 21awhich is located between the forward end of the rear casing component 25and a radially inward extension of the flange 30 at the forward end ofthe front casing component 24.

The intermediate liner or insert 22 is supported by the forward portionof the rear casing component 25 and at its forward end abuts the flange21a of the insert 21. The rear liner or insert 23 is supported by therear portion of the rear casing component 25 and is in abutting relationwith the liner 22. At its rearward end, the liner 23 abuts an intumedlip 25a afi'orded by the casing component 25. The insert 23 is formedwith an aperture 20a which registers with a corresponding aperture 20bformed in the rear portion of the rear casing component 25 collectivelyto define the opening 20 through which the molten metal can be pouredinto the interior of the bore 15.

As can be seen at 37, the external surface of the forward portion of therear casing component 25 is somewhat recessed so that there is a smallclearance space, extending over most of the length of the forwardportion of the front casing component. Additionally, whilst the internaldiameter of the rear casing component 25 is nominally unifonn throughoutits length, the diameter may be locally increased by a few thousandthsof an inch in the regions indicated at 38 and 39 so as to allow for asmall amount of outward expansion of the liners 22 and 23 in thoseregions and to prevent undue compressive stress being exerted on theseliners at the working temperature of the assembly.

The rate of heat loss from molten metal passing along the bore andsituated within the front liner or insert 21 is considerable, since heatis conducted therefrom to the die 10 and there is consequently atendency for a skin or solidified layer of metal to form immediatelyadjacent to the interior surface of the front liner or insert 21,particularly in the region indicated at 26. In the course of forwardmovement of the piston 17 this skin tends to be disrupted and pieces ofit may be forced outwardly to penetrate the inner surface of the frontliner or insert 21. Continued forward movement of the piston 17 tendsnevertheless to force these pieces forwardly dragging with themparticles of metal from the surface layer of the liner or insert 21leading to rapid erosion of this surface layer.

Accordingly, it is desirable that the front liner or insert 21 should bemade of a material which affords relatively low thermal conductivity inorder, so far as possible, to minimize the freezing of the metalundergoing casting and avoiding the formation of, or reducing thethickness of, the skin referred to. At the same time it is desirablethat the front liner or insert should be in contact with a heat sink sothat, despite the low thermal conductivity, heat is conveyed away fromthis component to an extent which prevents this component attaining sohigh a temperature that its properties of hardness are so adverselyaffected as to offset the value of the low thermal conductivity.Accordingly it is contemplated that the optimum values with respect tothermal conductivity and the capacity of the heat sink can be selected.

For casting ferrous metals it is contemplated that the front liner orinsert may be made of a ferrous metal and in particular a steel of acomposition designed to withstand abrasion under conditions of hightemperature. One steel suitable for this purpose is steel of thecomposition utilized for hot working forging dies, preferably thecomponent being subjected to hardening and nitriding. One particularlysuitable steel is that of A.I.S.l. specification H13. The composition ofthis steel is as follows carbon 0.3 to 0.4 percent, manganese 0.2. to0.4 percent, silicon 0.8 to 1.2, chromium 4.7 to 5.5 percent, vanadium0.8 to 1.2, molybdenum 1.2 to 1.75, balance iron.

Alternatively, the front liner or insert 21 .may be made of anon-ferrous metal. In this category, it is contemplated that therefractory metals might be utilized such as tungsten, platinum,molybdenum and their alloys, particularly an alloy of molybdenum knownby the designation TZM which contains 0.5 percent titanium and 0. 1percent zirconium.

Further alternative non-ferrous materials which might be employedinclude the so-called superalloys which are based on nickel and chromiumand the like, particularly those known as Rene 41 and Nimonic.

Another alternative material which may be employed for this component isa ceramic material. Particularly suitable ceramic for this purpose aresilicon nitride, and silicon carbide and zirconia. In this case theceramic material would be in the form of a liner supported externallyand maintained in a state of compression by an outer tube made forexample from a steel such as that mentioned above.

It would also be possible to employ materials of the type known ascermets" and comprising a mixture of ceramic and metallic components.

All of these materials have ability to maintain a reasonably hardsurface to define the bore 15 at the delivery station at the temperatureat which ferrous metals are required to be cast. Ceramic and cermetmaterials especially are also resistant to penetration by any pieces ofthe skin previously mentioned.

Any deficiency in the matter of transverse rupture strength would bemade good by the additional complement of transverse rupture strengthafforded by the front casing component 24, particularly the flange 30provided at the forward end thereof and which abuts the die 10 to whichit is secured by screws or other suitable fastening elements at theposition indicated at 31.

A further factor in the operating conditions is that the comer 27 formedat the junction of the interior surface and forward end surface of thefront liner or insert 21 is subjected to severe thermal shock and, tominimize failure from thermal fatigue, it is preferred that this comerbe rounded as shown. A typical radius when the bore 15 has an internaldiameter of about 1 percent inches would be one-eighth of an inch, theinsert 21 having a wall thickness of about one-fourth of an inch.

Additionally, on completion of the feeding operation, a plug 28 of metalremains in the bore 15 adjacent to the delivery station 18, such plugbeing positively expelled by the piston 17 upon solidification of thecast article in the die cavity 12. To facilitate expulsion of this plugand minimize wear on the surface of the bore, the terminal portion ofthe front liner or insert 21 is made of divergent form, as indicated at29. A typical divergence (measured as the semi angle of the cone) wouldbe 5, and the axial dimension over which such divergent is present wouldtypically be three-fourths of an inch for a bore of the diameterpreviously mentioned.

Instead of the forward extremity of the shot duct, in which thesolidified plug 28 forms, being formed as an integral part of the frontliner or insert 21, it could be structurally separate therefrom. Forexample, it could comprise an insert of molybdenum, or the alloy thereofmentioned above, keyed into the die so as to be replaceable;Alternatively, the die 10 itself might be shaped to' afford a partequivalent to the forward extremity of the insert 21 as shown. As afurther possibility, the front liner or insert 21 might be replacedentire-, ly by a bore formed in the die 10. g

The intermediate liner or insert 22 is subjected to somewhat differingconditions, in that the major problem in this case is one of thermalfatigue. Accordingly while any of the materials previously mentioned forpossible use in respect of the component 21 may be employed, it iscontemplated that advantageously steel of the A.I.S.I. specification H13may be best suited tothis component.

It will be noted, however, that in the event of employing a materialhaving low transverse rupture strength, for example one of the-ceramicmaterials mentioned, again any deficiency in the respect is made good bythe presence of both the front casing component 24 and the forwardportion 32 of the rear casing component 25 which are assembled inconcentric relacomponents, or by deliberately providing clearance spacesbetween them if desired, either along their whole lengths or at selectedpositions, so as to control the operating environment of theintermediate liner or insert 22.

In respect of the rear liner or insert 23, the conditions of operationagain differ, in that the observed area of maximum erosion occurs at thepoint of impact of the molten metal stream entering the bore 15 throughthe opening 20, this point of impact coinciding with the forward end ofthe arrow 33.

Erosion at this position is believed to be due partly to fluid frictionbut also to an appreciable extent by chemical and/or physical actionbetween the cast metal and that of which the component 23 is made(assuming that it is made of a metal).

7 chemical and/or physical reaction with the metal to be cast (forexample the component 23 may be made of molybdenum or tungsten or alloysthereof when casting a ferrous metal; or

b. by using a non-metallic material such as a cermet or one of theceramics already mentioned.

In either case any deficiency of transverse rupture strength would bemade good by the rearward portion of the rear casing component 25. Againthis-can closely embrace the rear liner or insert-23 along the entirelength of the latter, or radially spaces may'be left if desired tocontrol the rate of heat transfer in an outward radial direction.

It is particularly to be noted that whilst the materials of which theinserts 21, 22 and 23 are made are chosen respectively to suit thedifi'erent operational conditions encountered by these components, itis'possible in some cases for all three inserts to be made from the.

same material, especially H13 steel or the like, and for the servicelife of the shot duct thus formed to be materially improved relative toprior art shot ducts which are not divided into longitudinallysuccessive sections. Merely forming the shot duct in three or moresections is believed to improve the thermal stability of theconstruction and therefore prolong its service life, but where, as inthe embodiment illustrated,the liners are mounted in a casing,thepossibilityof controlling the rate of outward heat transfer asmentioned above further afl'ords an opportunity to ensure that theoptimum environmental conditions exist in all regions of the duct evenwhere all the liners are made of the same material. a

In particular it is to be noted thateven where components of the shotduct are formed from H13 steel it is possible to cast mild steel whichhas a higher melting point than H13 steel by suitable control of therate of outward heat transfer. Similarly it is possible to cast H13steel in a shot duct including components formed from H13 steel.

It will thus be seen that in accordance with the invention differenceregions of the shot duct may be formed from different materials and/orthe environmental conditions in different regions of the shot duct canbe controlled, particularly as regards the rate of outward heattransfer, to suite the particular requirements of the different regions.

The components described may be secured together in any suitable manneras, for example, by the provision of screws or other fastening elementat the position 34 extending through the flange 35 of the rear casingcomponent into threaded bores in the front casing component 24.

Particularly, where one or more of the liners or inserts is formed of aceramic material, or other material having a comparatively lowtransverse rupture strength, the casing may includean additionalsleevelike component which is in direct contact with the linersthroughout the whole length of the shot duct. In this case, the linerscollectively may present an external surface which tapers slightly fromend to end, preferably decreasing in cross-sectional dimensions in adirection from the receiving station towards the delivery stationalthough the opposite taper could be utilized. The additional casingcomponent would then be of complementary taper so as to be assembledwith the liners as a press fit so that the liner is supported by thecasing at all positions along its length.

However, it would be possible for the casing components to be omittedand for the shot duct to be formed from a plurality of longitudinallysuccessive components which are secured directly together without beingsupported by such a casing providing such components are designed toafford the requisite transverse rupture strength.

We claim:

1. In apparatus for casting ferrous metal comprising a. separablerepeatedly usable dies defining in combination a cavity;

b. means for moving said dies relatively towards and away from oneanother between open and closed positions;

c. an elongated shot duct having at one end a receiving station forreceiving shots at an operating temperature sufficient to provide themetal in molten condition and at its other end a delivery stationcommunicating with said cavity; and

d. a piston movable in said shot duct to feed said shots of molten metalinto said cavity;

the improvement wherein e. said shot duct comprises at least threecomponents, disposed in end to end relationship longitudinally of theshot duct, a first component being disposed at said delivery station andbeing formed of a material whose surface remains in hard solidified format the operating temperature resistant to penetration and abrasion as aresult of fragmentation and displacement of a solid state skin formed inthe metal during casting, a second component being disposed at thereceiving station and being made from a material which is free fromentering into chemical and physical reaction with the ferrous metalbeing cast, and at least one further component intermediate said firstand second components and being formed from a material resistant tothermal fatigue.

' 2. Apparatus according to claim 1 wherein said first component isformed of a material selected from the group comprising molybdenum, amolybdenum alloy, tungsten, a tungsten alloy; said second component isformed of a material selected from the group comprising molybdenum, amolybdenum alloy, tungsten, a tungsten alloy; and said intermediatecomponent is formed from a hot working die steel.

3. Apparatus according to claim 2 wherein said hot working die steel isa steel according to A.I.S.I. specification H13.

4. Apparatus according to claim 1 wherein a casing extendslongitudinally of said shot duct, and at least one of said components ismounted within said casing thereby providing said component withexternal suprt. 5. Apparatus according to claim 1 wherein said firstcomponent is located partly within one of said dies which has apredetermined longitudinal dimension, a

solid metal plug being formed within said first com-

1. In apparatus for casting ferrous metal comprising a. separablerepeatedly usable dies defining in combination a cavity; b. means formoving said dies relatively towards and away from one another betweenopen and closed positions; c. an elongated shot duct having at one end areceiving station for receiving shots at an operating temperaturesufficient to provide the metal in molten condition and at its other enda delivery station communicating with said cavity; and d. a pistonmovable in said shot duct to feed said shots of molten metal into saidcavity; the improvement wherein e. said shot duct comprises at leastthree components, disposed in end to end relationship longitudinally ofthe shot duct, a first component being disposed at said delivery stationand being formed of a material whose surface remains in hard solidifiedform at the operating temperature resistant to penetration and abrasionas a result of fragmentation and displacement of a solid state skinformed in the metal during casting, a second component being disposed atthe receiving station and being made from a material which is free fromentering into chemical and physical reaction with the ferrous metalbeing cast, and at least one further component intermediate said firstand second components and being formed from a material resistant tothermal fatigue.
 2. Apparatus according to claim 1 wherein said firstcomponent is formed of a material selected from the group comprisingmolybdenum, a molybdenum alloy, tungsten, a tungsten alloy; said secondcomponent is formed of a material selected from the group comprisingmolybdenum, a molybdenum alloy, tungsten, a tungsten alloy; and saidintermediate component is formed from a hot working die steel. 3.Apparatus according to claim 2 wherein said hot working die steel is asteel according to A.I.S.I. specification H13.
 4. Apparatus according toclaim 1 wherein a casing extends longitudinally of said shot duct, andat least one of said components is mounted within said casing therebyproviding said component with external support.
 5. Apparatus accordingto claim 1 wherein said first component is located partly within one ofsaid dies which has a predetermined longitudinal dimension, a solidmetal plug being formed within said first component during casting toextend partway along said longitudinal dimension, and said firstcomponent has a length greater than said longitudinal dimension.